New materials and scaffold fabrication method for nerve tissue engineering

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Abstract

Acetylcholine is a neurotransmitter that regulates neurite branching, induces neurite outgrowth, and synapse formation. Because of its various roles in neuronal activities, acetylcholine-based materials may also be useful in nerve repair. We present a series of biodegradable polymers with varying concentrations of acetylcholine-like motifs. We hypothesize that neurite sprouting and extension can be enhanced by using materials to present biochemical and physical cues.
Acetylcholine-like motifs were incorporated by the polycondensation of diglycidyl sebacate, aminoethyl acetate, and leucine ethyl ester, which permitted control over acetylcholine motif concentration. Interactions between the polymers and neurons were characterized using rat dorsal root ganglia explants (DRG). We screened the potential application of these materials in nerve tissue engineering using the following criteria: 1) neurite sprouting, 2) neurite length, and 3) distribution of the neurite lengths. The ability of DRG to sprout neurites was influenced by the concentration of acetylcholine motifs of the polymer. Addition of acetylcholine receptor antagonists to DRG cultured on the polymers significantly decreased neurite sprouting, suggesting acetylcholine receptors mediate sprouting on the polymers. Future studies may examine how neurons on acetylcholine-based polymers exhibit changes in downstream signaling events and cell excitability that are associated with receptor activation.
In preparation for testing the acetylcholine-based polymers in vivo, porous scaffolds with longitudinally oriented channels were fabricated using fiber templating and salt leaching. Micro computed tomography, scanning electron microscopy, and cryo-sectioning revealed the presence of longitudinally oriented channels. Channel volume and average pore size of the scaffolds were controlled by the number of fibers and salt fusion time. Future studies may involve testing the effect of acetylcholine-motifs by coating polymers onto such scaffolds or assessing the effect of the scaffold's dimensional properties on nerve regeneration.